Commit_operation bug

Dan Rathbun

Also do not use entities C++ collections directly, make a Ruby Array copy of them, when your loops need to delete items.
You cannot safely iterate and delete items from the C++ collections.
entsA = model.entities.to_a
or
entsA = group.entities.to_a
.

thomthom

Good point.

Dan Rathbun

In addition, some kind of begin .. rescue .. end structure might be used to trap errors, and call .abort_operation in the rescue clause(s), and maybe prevent the BugSplat!.

.. maybe something like this?


begin
  model.start_operation("Task",true)
  entsA = model.entities.to_a
  entsA.each do |e|
    # do stuff 
  end
  model.commit_operation
rescue
  model.abort_operation
end

Anyone have a better example of a basic "operational" block, with error trapping ??

thomthom

That's as simple, and classic, example as it gets.

Jim

I think that in order to catch all classes of exceptions, you need to explicitly give an argument to the rescue clause:


...
rescue Exception => e
puts e.message
puts e.backtrace
end

Or use the appropriate type of Exception, such as LoadError, etc. I don't know how you are supposed to know what type of exception to expect, though.

thomthom

Doesn't it do that be default?

Jim

Back on topic - i would guess, as Dan said, you are probably changing (deleting items from) the collection as you iterate it; which is a no-no.

Jim

I thought, with no argument, that rescue would catch Exceptions of type StandardError, which is probably what is wanted most of the time. But a LoadError and a SyntaxError would not be handled by default.

And I will add that I seem to have got in the habit of using the form I gave as an example, even though it may not be appropriate in all situations.

Dan Rathbun

I believe the rescue clauses' argument list works like the .kind_of? method, in that it is a conditional test that returns true for the exception class named, OR if the named class is a superclass of the actual exception class. (The testing begins at the actual class level, and "walks" the ancestry backward "up the family tree" of superclasses until it the named class is reached. Using Exception as the argument would always execute the rescue clause, as it is the ancestor of ALL exception subclasses.)

Multiple rescue clauses can be defined one after the other, similar to if ... elsif .. elsif ... else ... end statements.

Also more than one Exception class can be listed for each rescue clause.

Finally we can use the global $! to access the exception instead of creating a local via => var, but that's just a matter of personal style.

See: http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_exceptions.html

adabyron

Dan and Jim: No, I'm not deleting entities as I iterate over the C++ collection. I delete the entities using object attributes, that is, I have something like this:


class Shape

  attr_accessor ;group

  ...

  def erase()
    Sketchup.active_model.entities.erase @group
  end

end

At certain moment, I need to erase all the shapes, so I iterate over MY array of shapes:

shapes.each { |s|
  s.erase
}

thomthom: OK, I didn't know that heavy scripts often prevent the UI to refresh.

By the moment I'm happy with this behavior. Moreover, I have been told to refresh the UI, so the user can see the steps the algorithm is taking (how the entities are added and erased): I don't need to preserv performance any more. Everything is ok (no bug splats at all) when I don't use start_operation and commit_operation.

In case I need to preserv performance again, I will make use of the begin.. rescue.. endidea

Thank you very much

thomthom

But what about the undo stack? If you do not wrap your code in *_operation you get lots of small operations on your undo stack instead of one undoable step. Are you sure your users would be ok with this?

adabyron

thomthom: I have a command that resets the plugin, which users may use. By the moment I'm not worrying about the undo stack, but this is a future task...

But I have just realized one thing:

Sometimes, when I close SketchUp after using my plugin, I get a bug splat. Maybe it is probably due to the same reasons, I mean, when closing SU, the current operation commits, isn't it?

I didn't give it importance at the beginning, because I couldn't reproduce the conditions in which the bug arised... The fact is that, now I realize, everything is OK if I don't delete entities. I have always thought that the bug was some consequence of using EntitiesObservers.

I have some groups.entities in my plugin with this kind of observers attached, but these groups aren't the ones I delete inside the previous affected code. When I need to erase them (outside this code), I check if they have an attached observer and in that case I first remove the observer and then I erase the group.

I have also an EntitiesObserver attached to Sketchup.active_model.entities, which only defines the onElementModified method. This method only does something when the modified entity ID is inside an internal list (there are few entities inside this list).

These observers don't make changes inside the model. Anyway, might them be the source of all my problems?

thomthom

hmm... if you don't modify the model from within the events you usually should be fine. ..but there might be deviating causes. observers has always been a can of worms.

I've tried to make an overview: http://forums.sketchucation.com/viewtopic.php?f=180&t=30793

So - they could be the cause.

Maybe we could get the attention of a Googler to look at this thread...

adabyron

Ok, they ARE the problem.

I have just checked what happens if I don't attach an observer to Sketchup.active_model.entities, and everything is fine with *_operation.

But I still have bug splats when closing SU. I bet this problem has to do with the other EntitiesObservers...

By the moment I need this observers, so I will have to resign myself until the observers run smoothly...

By the way, your overview was so useful to me some weeks ago (I was struggling with another bug). It is a great job

Thank you

thomthom

Which observers and which events did you use?
Can you also briefly describe what you do with the events?
(It'd be nice ot have this info in order to attempts to correlate the issues.)

Btw - I just tried abort_operation to write out texture without adding to the undo stack or messing with the outliner:


tw = Sketchup.create_texture_writer
model = Sketchup.active_model

model.start_operation('Write Textures', true)

tmp = model.definitions.add('Temp_TextureWriter')
g = tmp.entities.add_group
model.materials.to_a.each_with_index { |m,i|
  next if m.texture.nil?
  g.material = m
  tw.load( g )
  p tw.write( g, "c;/temp/mat_#{i}.png" )
}

model.abort_operation

Notice that I make a temp component definition - and therefore do not add anything to the model's entities collection. In worst case you just end up with a temp definition with an empty group. which I think SU will purge automatically at some point.
The code can be improved with error catching - but the concept works.

Think I'll make a wrapper for doing things like this - calling a method with a block where everything inside the block is aborted and therefore not included in the undo stack.

adabyron

Ok, I have three types of observers:

Type 1 < AppObserver

Attached to Sketchup. It defines:

-onQuit, that asks the user to save certain structure of my plugin

-onNewModel, that does the same as onQuit plus hiding the plugin toolbar

-onOpenModel, that does the same as onNewModel

Type 2 < EntitiesObserver

This one is attached to Sketchup.active_model.entities at the beginning of the code. It defines:

-onElementModified, that checks if the modified entity is included in an internal list. In that case, shows a messagebox.

Type 3 < EntitiesObserver

This is attached to some special entities in my application. I have to save the transformations that the user performs on them. It defines:

-onElementModified, that saves the transformation and material of the modified entity

-onEraseEntities, that shows a messagebox

-onElementRemoved, that shows a messagebox

thomthom

@adabyron said:

This one is attached to Sketchup.active_model.entities at the beginning of the code. It defines:

What if something is contained in a group/component?

@adabyron said:

-onElementModified, that saves the transformation and material of the modified entity

"Save" - saving a reference to the material object?

And all of these message boxes - all they do is display a message? Nothing that is done depending on how the user interacts with the messagebox?

adabyron

@thomthom said:

What if something is contained in a group/component?

I don't understand what you mean. I have an internal list of entity IDs (they are groups), and if the modified entity ID is inside this list, I show a message box.

@thomthom said:

"Save" - saving a reference to the material object?

Yes, and the transformation one.

@thomthom said:

And all of these message boxes - all they do is display a message? Nothing that is done depending on how the user interacts with the messagebox?

Nothing. Just messages.

thomthom

@adabyron said:

I don't understand what you mean. I have an internal list of entity IDs (they are groups), and if the modified entity ID is inside this list, I show a message box.

You monitor model.entities - but are you sure the entities you want to monitor is always in model.entities and not wrapped in some other group / component?
You don't have to monitor when the active context changes and hook your observer to model.active_entities?

adabyron

Yes, I'm sure. The entities I want to monitor are always added to Sketchup.active_model.entities.